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<html>

<head>
  <meta charset='utf-8'>
  <meta name='viewport' content='width=device-width, initial-scale=1, user-scalable=no'>
  <meta name='mobile-web-app-capable' content='yes'>
  <meta name='apple-mobile-web-app-capable' content='yes'>
  <link rel='icon' type='image/png' sizes='32x32' href='../favicon-32x32.png'>
  <link rel='icon' type='image/png' sizes='96x96' href='../favicon-96x96.png'>
  <link rel='stylesheet' href='../css/common.css'>

  <title>Equirect Layer</title>
  <!-- Stereo layer dependency -->
  <script src="../js/wglu/wglu-program.js"></script>
  <script src="../js/wglu/wglu-url.js"></script>
  <script src="../js/stereo-util.js"></script>
</head>

<body>
  <header style="max-width: 800px;">
    <details open>
      <summary>Equirect Layer</summary>
      <p>
        This sample shows how to draw a scene into an equirect layer.
        Equirect layers are similar to projection layers in terms of their advantages.
        They can be used for rendering static backgrounds like cube layers,
        but because it maps a square-shaped image over a sphere,
        distortion is required to correctly render objects.
        This is fine for rendering dedicated 360 images, but if we want
        to add objects to the background, we will need to apply distortion
        to these objects to ensure they are rendered correctly, whereas
        using cube layer can eliminate this process. Thus, the real edge
        of using an equirect layer over cube layer is to show 180/360 video.
        <a class="back" href="./index.html">Back</a>
      </p>
      <input type="checkbox" id="eqrtIsStereo">Stereo equirect layer</input><br />
      <input type="checkbox" id="eqrtIs180">180 degree equirect</input><br />
    </details>
  </header>
  <main style='text-align: center;'>
    <p>Click 'Enter VR' to see content</p>
  </main>
  <script type="module">
    import { WebXRButton } from '../js/util/webxr-button.js';
    import { Scene, WebXRView } from '../js/render/scenes/scene.js';
    import { Renderer, createWebGLContext } from '../js/render/core/renderer.js';
    import { QueryArgs } from '../js/util/query-args.js';

    const EQRT_TEXTURE_MONO_PATH = '../media/textures/mono_equirect_test.png';
    const EQRT_180_TEXTURE_MONO_PATH = '../media/textures/mono-equirect180.png';
    const EQRT_TEXTURE_STEREO_PATH = '../media/textures/chess-pano-4k.png';
    const EQRT_180_TEXTURE_STEREO_PATH = '../media/textures/chess-pano-4k180.jpg';

    // If requested, use the polyfill to provide support for mobile devices
    // and devices which only support WebVR.
    import WebXRPolyfill from '../js/third-party/webxr-polyfill/build/webxr-polyfill.module.js';
    if (QueryArgs.getBool('usePolyfill', true)) {
      let polyfill = new WebXRPolyfill();
    }

    // XR globals.
    let xrButton = null;
    let xrSession = null;
    let xrRefSpace = null;
    let xrGLFactory = null;
    let xrFramebuffer = null;
    let stereoUtil = null;

    // WebGL scene globals.
    let gl = null;
    let renderer = null;
    let scene = new Scene();

    // Layer globals
    let projLayer = null;
    let eqrtLayer = null;
    let eqrtImageElement = null;
    let eqrtIsStereo = false;
    let eqrtIs180 = false;
    let eqrtTextureWidth = 0;
    let eqrtTextureHeight = 0;
    let eqrtRadius = 10;

    function initXR() {
      xrButton = new WebXRButton({
        onRequestSession: onRequestSession,
        onEndSession: onEndSession
      });
      document.querySelector('header').appendChild(xrButton.domElement);

      if (navigator.xr) {
        navigator.xr.isSessionSupported('immersive-vr').then((supported) => {
          xrButton.enabled = supported;
        });
      }
    }

    function onRequestSession() {
      if (!xrSession) {
        navigator.xr.requestSession('immersive-vr', {
          requiredFeatures: ['layers'],
        }).then(onSessionStarted);
      } else {
        onEndSession();
      }
    }

    function initGL() {
      if (gl) { return; }
      gl = createWebGLContext({ xrCompatible: true, webgl2: true, });
      document.body.appendChild(gl.canvas);
      gl.clearColor(0.0, 0, 0, 0.0);

      function onResize() {
        gl.canvas.width = gl.canvas.clientWidth * window.devicePixelRatio;
        gl.canvas.height = gl.canvas.clientHeight * window.devicePixelRatio;
      }
      window.addEventListener('resize', onResize);
      onResize();

      renderer = new Renderer(gl);
      scene.setRenderer(renderer);

      // Util for rendering stereo layers
      stereoUtil = new VRStereoUtil(gl);
    }

    // Called when we've successfully acquired a XRSession. In response we
    // will set up the necessary session state and kick off the frame loop.
    function onSessionStarted(session) {
      xrSession = session;
      scene.inputRenderer.useProfileControllerMeshes(session);
      session.addEventListener('end', onSessionEnded);

      initGL();

      xrFramebuffer = gl.createFramebuffer();
      xrGLFactory = new XRWebGLBinding(session, gl);

      eqrtIsStereo = document.getElementById("eqrtIsStereo").checked;
      eqrtIs180 = document.getElementById("eqrtIs180").checked;
      let eqrtImagePath = eqrtIsStereo ?
        (eqrtIs180 ? EQRT_180_TEXTURE_STEREO_PATH : EQRT_TEXTURE_STEREO_PATH) :
        (eqrtIs180 ? EQRT_180_TEXTURE_MONO_PATH : EQRT_TEXTURE_MONO_PATH);

      session.requestReferenceSpace('local').then((refSpace) => {
        xrRefSpace = refSpace;
        projLayer = xrGLFactory.createProjectionLayer({ space: refSpace, stencil: false });
        session.updateRenderState({ layers: [projLayer] });

        // Loading texture is async, create layer and update render state when done
        let imageElement = document.createElement('img');
        imageElement.src = eqrtImagePath;
        imageElement.onload = function () {
          eqrtTextureWidth = imageElement.width;
          eqrtTextureHeight = imageElement.height;
          eqrtImageElement = imageElement;
          eqrtLayer = xrGLFactory.createEquirectLayer({
            space: refSpace,
            viewPixelWidth: eqrtTextureWidth,
            viewPixelHeight: eqrtTextureHeight / (eqrtIsStereo ? 2 : 1),
            layout: eqrtIsStereo ? "stereo-top-bottom" : "mono",
          });

          eqrtLayer.centralHorizontalAngle = Math.PI * (eqrtIs180 ? 1 : 2);
          eqrtLayer.upperVerticalAngle = Math.PI / 2.0;
          eqrtLayer.lowerVerticalAngle = -Math.PI / 2.0;
          eqrtLayer.radius = eqrtRadius;
          session.updateRenderState({ layers: [eqrtLayer, projLayer] });
        }

        session.requestAnimationFrame(onXRFrame);
      });
    }

    function onEndSession() {
      xrSession.end();
    }

    function onSessionEnded(event) {
      if (event.session.isImmersive) {
        xrButton.setSession(null);
      }
      xrSession = null;
      gl = null;
    }

    function onXRFrame(time, frame) {
      let pose = frame.getViewerPose(xrRefSpace);
      xrSession.requestAnimationFrame(onXRFrame);

      if (eqrtLayer && eqrtLayer.needsRedraw) {
        let glayer = xrGLFactory.getSubImage(eqrtLayer, frame);

        // TEXTURE_CUBE_MAP expects the Y to be flipped for the faces and it already
        // is flipped in our texture image.
        gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);
        gl.bindTexture(gl.TEXTURE_2D, glayer.colorTexture);
        gl.texSubImage2D(gl.TEXTURE_2D, 0, 0, 0, gl.RGBA, gl.UNSIGNED_BYTE, eqrtImageElement);
        gl.bindTexture(gl.TEXTURE_2D, null);
      }

      if (pose) {
        gl.bindFramebuffer(gl.FRAMEBUFFER, xrFramebuffer);
        scene.updateInputSources(frame, xrRefSpace);

        let views = [];
        for (let view of pose.views) {
          let viewport = null;
          let glLayer = xrGLFactory.getViewSubImage(projLayer, view);
          glLayer.framebuffer = xrFramebuffer;
          viewport = glLayer.viewport;
          gl.bindFramebuffer(gl.FRAMEBUFFER, xrFramebuffer);
          gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, glLayer.colorTexture, 0);
          gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.TEXTURE_2D, glLayer.depthStencilTexture, 0);
          views.push(new WebXRView(view, glLayer, viewport));
        }
        scene.drawViewArray(views);
      }
      scene.endFrame();
    }

    initXR();
  </script>
</body>

</html>
